Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755379AbbB0UJW (ORCPT ); Fri, 27 Feb 2015 15:09:22 -0500 Received: from mail-yk0-f170.google.com ([209.85.160.170]:43548 "EHLO mail-yk0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755119AbbB0UJV (ORCPT ); Fri, 27 Feb 2015 15:09:21 -0500 From: Pranith Kumar To: Catalin Marinas , Will Deacon , Steve Capper , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org (open list) Subject: [RFC PATCH] arm64: cmpxchg.h: Bring ldxr and stxr closer Date: Fri, 27 Feb 2015 15:09:17 -0500 Message-Id: <1425067776-2794-1-git-send-email-bobby.prani@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2509 Lines: 78 ARM64 documentation recommends keeping exclusive loads and stores as close as possible. Any instructions which do not depend on the value loaded should be moved outside. In the current implementation of cmpxchg(), there is a mov instruction which can be pulled before the load exclusive instruction without any change in functionality. This patch does that change. Signed-off-by: Pranith Kumar --- arch/arm64/include/asm/cmpxchg.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h index cb95930..8057735 100644 --- a/arch/arm64/include/asm/cmpxchg.h +++ b/arch/arm64/include/asm/cmpxchg.h @@ -89,8 +89,8 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, case 1: do { asm volatile("// __cmpxchg1\n" - " ldxrb %w1, %2\n" " mov %w0, #0\n" + " ldxrb %w1, %2\n" " cmp %w1, %w3\n" " b.ne 1f\n" " stxrb %w0, %w4, %2\n" @@ -104,8 +104,8 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, case 2: do { asm volatile("// __cmpxchg2\n" - " ldxrh %w1, %2\n" " mov %w0, #0\n" + " ldxrh %w1, %2\n" " cmp %w1, %w3\n" " b.ne 1f\n" " stxrh %w0, %w4, %2\n" @@ -119,8 +119,8 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, case 4: do { asm volatile("// __cmpxchg4\n" - " ldxr %w1, %2\n" " mov %w0, #0\n" + " ldxr %w1, %2\n" " cmp %w1, %w3\n" " b.ne 1f\n" " stxr %w0, %w4, %2\n" @@ -134,8 +134,8 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, case 8: do { asm volatile("// __cmpxchg8\n" - " ldxr %1, %2\n" " mov %w0, #0\n" + " ldxr %1, %2\n" " cmp %1, %3\n" " b.ne 1f\n" " stxr %w0, %4, %2\n" @@ -166,11 +166,11 @@ static inline int __cmpxchg_double(volatile void *ptr1, volatile void *ptr2, VM_BUG_ON((unsigned long *)ptr2 - (unsigned long *)ptr1 != 1); do { asm volatile("// __cmpxchg_double8\n" + " mov %w0, #0\n" " ldxp %0, %1, %2\n" " eor %0, %0, %3\n" " eor %1, %1, %4\n" " orr %1, %0, %1\n" - " mov %w0, #0\n" " cbnz %1, 1f\n" " stxp %w0, %5, %6, %2\n" "1:\n" -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/